PURPOSE: To attain oscillation control effective to an oscillation frequency deciding element having a region where temperature compensation is difficult at a temperature compensation voltage against temperature change by providing an A/D conversion means, a control data storage means and an oscillation control means.

CONSTITUTION: A temperature sensing element 3 detects an environmental temperature of a crystal oscillator 2 in an oscillation circuit 1 and a detection signal Va is outputted to an A/D converter 5. The converter 5 converts a signal Va into a digital signal, which is given to a ROM 6. The ROM 6 outputs a control data in response to the inputted digital signal to an oscillation control circuit 7. The circuit 7 is constituted by a switch Sn (n is 0, 1, 2...) and edits a capacitor Cn in response to the control data. The edited capacitor Cn is coupled with a terminal 1a of the circuit 1, the oscillator 2 controls the oscillation in response to the capacitor Cn and a corresponding oscillation signal is outputted to the control data from a terminal 1b. Thus, the oscillation is controlled effectively to the oscillation frequency deciding element having a region difficult for the temperature correction.